1. Field of the Invention
The present invention relates to a combination headlamp which contains at least two headlamps with reflectors housed in a lamp chamber.
2. Related Art
A conventional headlamp of this type as disclosed in Unexamined Japanese Patent Application No. Hei 2-162602, for example. As illustrated in FIGS. 1 and 2, the publication discloses a combination headlamp in which two projection lamps 3 and 4 are contained in a lamp chamber defined by a lamp body 1 and a front lens 2. Each of the projection lamps 3 and 4 consists of a single unit structure constructed by coupling together an elliptic reflector a, which contains a light source located at the first focal point, and a projection lens b by a tubular lens holder c. The projection lamp 4 is a lamp only for main beams, and the projection lamp 3 is a lamp for both main beams and sub-beams. A shade e for clear-cut line formation is disposed in a lens holder c of the projection lamp 3. The front lens 2 mounted in the front opening of the lamp body 1 is made of synthetic resin and shaped like a capsule. The front lens 2 has circular areas 2a and 2b corresponding to the projection lamps 3 and 4. Each circular area extends to the front from a step 2c.
Thus, the headlamp contains two lamps 3 and 4 in the lamp chamber. Because of this, the headlamp is larger in size than the headlamp of the type in which a single lamp is contained in the lamp chamber. Also, the front lens 2 is large in area. The front lens of the conventional combination headlamp as described above is substantially flat in shape, and simply a two-dimensional expansion of the front lens of the headlamp of the single-lamp type. Therefore, it is easily deformed when it receives an impact or shock.
When the combination headlamp of the two-lamp type is compared with an array of two headlamps each of the single-lamp type, the former requires a smaller space occupied by one lamp than the latter, because the former is more compact in size. When the two lamps are simultaneously lit, e.g., in a main beam mode, temperature increases dramatically in the lamp chamber, and the front lens becomes highly susceptible to thermal deformation.